A two-year-old has been identified as a potential victim of forced marriage, according to the Foreign Office.

The child, believed to be the youngest ever victim at risk of forced marriage in the UK, was among 250 children helped by a governmental specialist unit last year.

The Forced Marriage Unit, a joint initiative of the Foreign Office and Home Office, is able to intervene where there is a belief that a child under 18 could be a victim.

Carla Thomas, head of the unit, said that cases with very young victims involved the promise of future marriage.

The unit gave advice or support in 1,485 cases last year, according to its latest statistics, which showed that 16 to 25-year-olds were most at risk of being forced into marriage. The oldest victim was 71.

The unit can report cases involving children under 18 to social services, which has a responsibility to safeguard the child. Civil courts also have the power to issue forced marriage protection orders to stop weddings taking place.

The 1,485 cases known to the unit last year involved 60 different countries – 47% involved Pakistan, 11% Bangladesh and 8% India. More than 80% of the victims were female.

Outside Britain the unit's work often involves embassy staff trying to rescue victims who may have been held captive and forced into getting married.

The unit also said there were 114 cases involving people with disabilities, and 22 involving those who identified as gay, lesbian, bisexual or transgender.

Jeremy Browne, the Home Office minister, said the figures showed an alarming number of victims whom it was vital to protect: "Forced marriage is a devastating form of abuse that is absolutely unacceptable in our society."

David Cameron has pledged to make forced marriage a criminal offence in England and Wales. Ministers hope legislation will be brought forward in 2013 or 2014.